Abstract: The invention has an object to provide a disk evaluation apparatus capable of performing a highly reliable disk evaluation even on a recording disk on which information is recorded in high density. Amplitude-limited read sample value sequence are obtained by limiting read sample value sequence to a predetermined amplitude limit value, the read sample value sequence obtained by sampling a read signal read out from the recording disk as timed to a clock having the same frequency as that of a channel clock. Where a gap between a maximum sample value and a minimum sample value of the amplitude-limited read sample value sequence is equivalent to a predetermined distance of high-frequency wavelength, the maximum sample value and the minimum sample value are increased thereby to obtain high-frequency enhanced read sample value sequence enhanced at the high region thereof.

Abstract: A pick up irradiates light beams at specified intervals in the tangential direction of the main track to be reproduced and both of adjacent tracks on a disk 10 on which tracks are formed. A CTC unit 15 uses the delay amount ?d of the respective sample-value series corresponding to the reproduction signal RFm from the main track and reproduction signals RF1, RF2 from both adjacent tracks to correct the delay, then outputs a CTC output signal from which the cross-talk component has been removed. In addition, when adjusting the delay, the CPU 17 applies a disturbance to the control signal for the actuator of the servo-control unit 18 and changes the delay amount ?d within a specified range of change. At this time, the CPU 17 sets the delay amount ?d, which minimizes the jitter value found by the jitter detection unit 16 according to the CTC output signal, for the CTC unit 15. This makes it possible to set the optimum delay amount ?d when adjusting the delay, even when there is little steady cross-talk.

Abstract: In a cross-talk canceller (CTC) that removes the cross-talk from the adjacent tracks that is contained in the reproduction signal from the main track, a sample-value series S1? for the reproduction signal from the adjacent track is input to a correlation-detection unit to find its correlation with the signal pattern of the signal output from the CTC that is detected by a pattern-detection unit, and then it passes through one of the correction-coefficient units that is connected by the switch and then integrated by the integrator, and the tap coefficient used by the variable filter of the CTC is obtained to a narrow control frequency zone.

Abstract: The invention has an object to provide a disk evaluation apparatus capable of performing a highly reliable disk evaluation even on a recording disk on which information is recorded in high density. Amplitude-limited read sample value sequence are obtained by limiting read sample value sequence to a predetermined amplitude limit value, the read sample value sequence obtained by sampling a read signal read out from the recording disk as timed to a clock having the same frequency as that of a channel clock. Where a gap between a maximum sample value and a minimum sample value of the amplitude-limited read sample value sequence is equivalent to a predetermined distance of high-frequency wavelength, the maximum sample value and the minimum sample value are increased thereby to obtain high-frequency enhanced read sample value sequence enhanced at the high region thereof.

Abstract: A clock generator in a recorded information reproduction apparatus for reproducing recorded information from a recording medium includes a pickup that produces a reading signal by reading a recording track of the recording medium. The reading signal is sampled by a sampling circuit at timing corresponding to a clock signal to produce a reading sample value sequence. A crosstalk removing circuit removes crosstalk components which are present in recording tracks adjacent to the recording track read by the pickup from the reading sample value sequence and produces a crosstalk-removed reading sample value sequence. A phase detecting circuit detects a phase error existing in the reading signal based on the crosstalk-removed reading sample value sequence. A clock signal generating circuit generates the clock signal based on the phase error.

Abstract: In the case of delaying any one of the detected signals, which are optically obtained from a plurality of trucks, in which the information are respectively recorded under a state that the DC component is removed, a zero cross waveform is extracted from a main detected signal, which is obtained from a main truck. Then, a sub detected signal obtained from a sub truck is held at a timing at which this zero cross waveform is extracted. Further, a sub detected signal, which has been held during a predetermined time frame, is averaged. Moreover, delay amounts with respect to the sub detected signal and the main detected signal are calculated by comparing a waveform of the averaged sub detected signal and the zero cross waveform. Then, the present sub detected signal and the main detected signal are delayed by the calculated delay amounts.

Abstract: There is disclosed a crosstalk removal apparatus in which a main track, one adjacent track, and the other adjacent track in a disk with the tracks formed therein are irradiated with light beams at predetermined intervals in a tangent direction by a pickup. A CTC unit uses delay amounts of respective sample value series corresponding to a reproduction signal of the main track and those of the adjacent tracks to correct delays, and outputs a CTC output signal from which a crosstalk component is removed. A wobble signal detector detects wobble signals of the respective tracks based on a push-pull output of the disk, and a delay circuit controller obtains optimum delay amounts based on a phase relation of the respective wobble signals and sets the delay amounts in the CTC unit.

Abstract: A tracking controller capable of conducting a correct tracking control even if a recording track is formed with a narrow track pitch on a recording disk. The tracking controller calculates an error value between a read signal read from a recording track intended for reading and a predetermined value, a first coefficient from a correlation between a read signal read from a recording track adjacent to the recording track intended for reading on the inner peripheral side of the disk and the error value, and a second coefficient from a correlation between a read signal read a recording track adjacent to the recording track intended for reading on the outer peripheral side of the disk and the error value. A difference between the first and second coefficients is calculated as a tracking offset which is subtracted from a tracking error to correct a tracking offset.

Abstract: A signal delay apparatus is provided with; a FIR filter for detecting a leakage signal, which is mixed in a digital detected signal, which is optically obtained from a main truck to be detected in association with the information recorded on a sub truck adjacent to the main truck to be detected, based n a filter coefficient; a coefficient setting unit for generating the above filter coefficient based on the digital detected signal, of which leakage signal is removed, and a digital detected signal, and outputting the generated filter coefficient to the filter; a CPU for controlling the delay amount in the delay with respect to any filter coefficient based on the change of the filter coefficient, which is generated in a predetermined time period and variable delay circuits and for delaying the digital detected signal and the digital detected signal by the controlled delay amount.

Abstract: A waveform equalizer which can improve a quality of a read signal by certainly correcting asymmetry in the read signal and a data reproducing apparatus using the waveform equalizer. The waveform equalizer performs a waveform equalization to the read signal and is constructed by: inclination discriminating means for detecting an ascending slope portion and a descending slope portion of the read signal; a filter for performing a filtering process to the read signal; and characteristics switching means for switching frequency characteristics of the filter in accordance with a discrimination output of the inclination discriminating means.

Abstract: A recorded information reproducing apparatus has a crosstalk canceler to ensure fast convergence of the values of filter coefficients of an adaptive digital filter and stable operation. The recorded information reproducing apparatus comprises a reading unit for reading recorded information from one track on a recording medium to acquire a first read signal, and for reading recorded information from at least one track adjacent to the one track to acquire a second read signal; an operating unit for operating at least one coefficient on the second read signal; a subtracter for subtracting an output of the operating unit from the first read signal; and a coefficient setting unit for setting the at least one coefficient and for restricting the at least one coefficient in such a way that the at least one coefficient becomes greater than a first predetermined value or smaller than a second predetermined value.

Abstract: There is disclosed a crosstalk removal apparatus in which a main track, one adjacent track, and the other adjacent track in a disk with the tracks formed therein are irradiated with light beams at predetermined intervals in a tangent direction by a pickup. A CTC unit uses delay amounts of respective sample value series corresponding to a reproduction signal of the main track and those of the adjacent tracks to correct delays, and outputs a CTC output signal from which a crosstalk component is removed. A wobble signal detector detects wobble signals of the respective tracks based on a push-pull output of the disk, and a delay circuit controller obtains optimum delay amounts based on a phase relation of the respective wobble signals and sets the delay amounts in the CTC unit.

Abstract: In a cross-talk canceller (CTC) that removes the cross-talk from the adjacent tracks that is contained in the reproduction signal from the main track, a sample-value series S1′ for the reproduction signal from the adjacent track is input to a correlation-detection unit to find its correlation with the signal pattern of the signal output from the CTC that is detected by a pattern-detection unit, and then it passes through one of the correction-coefficient units that is connected by the switch and then integrated by the integrator, and the tap coefficient used by the variable filter of the CTC is obtained to a narrow control frequency zone.

Abstract: A pick up irradiates light beams at specified intervals in the tangential direction of the main track to be reproduced and both of adjacent tracks on a disk 10 on which tracks are formed. A CTC unit 15 uses the delay amount &Dgr;d of the respective sample-value series corresponding to the reproduction signal RFm from the main track and reproduction signals RF1, RF2 from both adjacent tracks to correct the delay, then outputs a CTC output signal from which the cross-talk component has been removed. In addition, when adjusting the delay, the CPU 17 applies a disturbance to the control signal for the actuator of the servo-control unit 18 and changes the delay amount &Dgr;d within a specified range of change. At this time, the CPU 17 sets the delay amount &Dgr;d, which minimizes the jitter value found by the jitter detection unit 16 according to the CTC output signal, for the CTC unit 15.

Abstract: When the present invention is applied to a DVD recording apparatus, a data-frame generation circuit puts input user data into frames and a scramble circuit scramble the data using Maximum-length sequences, then an ECC block construction unit constructs ECC blocks and a RLL (1, 7) modulation unit performs RLL modulation to generate recording data. In addition, in the scramble circuit, Maximum-length sequences generation circuit generates preset Maximum-length sequences and a conversion circuit selectively converts this Maximum-length sequences to different random series based on recording position data for the position on the disk, then an EXOR circuit takes the exclusive OR of the input data and the converted random series to scramble the input data, making it possible to perform highly reliable scrambling with little correlation between pairs of adjacent tracks on the disk.

Abstract: The output bits that are shifted in order in the direction from stage R0 to R13 of a 14-stage shift register select Maximum-length sequences, which are generated by a specific primitive polynomial that correspond to a scramble number, from a selection table based on disk position data. Moreover, three selection bits are output according to the connection relationship with the selected Maximum-length sequences, and after the exclusive OR has been taken in order by the EXOR circuit, they are fed back to the initial stage R0. The recording data are scrambled by using the Maximum-length sequences that are generated in this way, making it possible to perform scrambling with little correlation and high reliability regardless of the recording position.

Abstract: A tracking control method and a tracking control apparatus in a recorded information reproducing apparatus which can execure an accurate tracking control even if recording tracks formed on a recording disk have a narrow track pitch. A tracking offset component is detected based on a balance between crosstalk amounts from the recording tracks adjacent to both sides of the recording track serving as a reading target and is subtracted from a tracking error signal, thereby performing a tracking offset correction.

Abstract: In the case of delaying any one of the detected signals, which are optically obtained from a plurality of trucks, in which the information are respectively recorded under a state that the DC component is removed, a zero cross waveform is extracted from a main detected signal, which is obtained from a main truck. Then, a sub detected signal obtained from a sub truck is held at a timing at which this zero cross waveform is extracted. Further, a sub detected signal, which has been held during a predetermined time frame, is averaged. Moreover, delay amounts with respect to the sub detected signal and the main detected signal are calculated by comparing a waveform of the averaged sub detected signal and the zero cross waveform. Then, the present sub detected signal and the main detected signal are delayed by the calculated delay amounts.

Abstract: A signal delay apparatus is provided with; a FIR filter for detecting a leakage signal, which is mixed in a digital detected signal, which is optically obtained from a main truck to be detected in association with the information recorded on a sub truck adjacent to the main truck to be detected, based n a filter coefficient; a coefficient setting unit for generating the above filter coefficient based on the digital detected signal, of which leakage signal is removed, and a digital detected signal, and outputting the generated filter coefficient to the filter; a CPU for controlling the delay amount in the delay with respect to any filter coefficient based on the change of the filter coefficient, which is generated in a predetermined time period and variable delay circuits and for delaying the digital detected signal and the digital detected signal by the controlled delay amount.

Abstract: An optical pickup for reading information recorded on information tracks of a recording medium by using a main light beam and a subsidiary light beam includes a diffraction device for diffracting an original light beam to generate the main light beam and the subsidiary light beam. The main light beam is applied to a reading track which is one of the information tracks on which the information to be read is recorded. The subsidiary light beam is applied to the information track adjacent to the reading track.